Process of preparing surface finishings



Patented May 22, 1951 2,554,471 rRocEs's or REPARING SURFACE FINISHINGS Donald Patterson, Darieii, F.

Turner, Stamford, Conn.; assign'ors to men,- can Cyanamid Company; New York, N. Y1; a

corporation of Maine No Drawing. Ajaplicationflctober 25, 1946, Serial No. 705,798

8 Claims.

This invention relates to surface finishings for wood and other hardboard materials, and a process of preparing the same; More specifically, the invention relates to high quality, clear, smooth, glossy and durable plastic finishes for wood Surfaces, and a process of applying the same. V

The process of this invention saves considerable time and labor in producing high quality finishes; To produce such finish with conventional methods would require from 3 to 8 'applications or coats of finishing composition with sanding, rubbing and polishing operations after each coating, "as well as considerable drying pe ri'ods between each coat. Such a lengthy, detailed procedure is notrequired by the process of this invention to produce superior surfaces. Further, this invention may be practical at relatively low pressures, which olfers many advantages over high pressure methods utilizing condensa-tion type thermosetting resins in that larger sized panels can be produced on the simpler presses, softer woods can be employed, and the natural color of light type woods can be retained- A further advantage of the process is that thicker veneers can be used for cigarette-proof surfaces due t) the increased heat resistanceof the surfaces. Likewise, harder resins andthicker surface films can be used because of the fiber reinforcements. The surface obtained by the process offers marked improvement in general durability and stain resistance over conventional surface coatings. The surface obtained or produced by this invention is superior in quality to the finest finishes produced with conventional surface coatings.

The surface produced by this invention is more durable than conventional wood finishes, particularly for household furnishings, in that it has excellent resistance to organic solvents such as butyl acetate found in nail polish remover, organic acids such as citric acid and acetic acid, soap solutions, hot cooking fat, boiling water and heat. It also offers better color and color stability than condensation type resins used at higher pressures forsurfacing wood, thus permitting the use of'softer and lighter woods.

One embodiment of this invention includes coating a polished steel press plate'with a thermosetting un'saturatedpolyester resin, smoothing a ply of specially selected paper thereon, heating this assembly to gel or partially polymerize the resin, coating the wood to be surfaced and gelling the resin and then pressing the plate on the wood at approximately 100 to 200 p, s. i. for 15 to 30 minutes at a temperature of 105 C. The pressed 5 2 assembly may be removed from the press and stripped from the plate without 'wait for The press to cool. The surface obtained in her is hard, transparent,fand requires '0 treatment, such as polishing operations and like. The surface finish "may be rubbed, h ever, with pumice and oil to produce a dull finisl'i Without destroying its transparent quality. 139 like token, the surface may be embossed b' u embossed plates in the pressing operatic process has been found satisfactory withu ed woods as we'llas' woods which haven ablystained and filled. If it is desired duce surfaces havingexcell'ent heatfresist'ance and cigarette-proof for table tops andthe likajfa thin sheet of metallic foil, such as 'aluininm, may be incorporated in the assembly beneat i'the to'pwood veneer prior to surfacing. It may be further noted that the finish can be applie'cl lt'o plywood simultaneously with the gluing of the veneers,- i e.; when the plywood is made. I

Although it is not always necessary, it "is frequently desirable to use a parting agent on the press plate prior to coating with the resin and pre e- L Suitable resins that may be employed in preqticing this my uqn are the unsaturated, polyeste'r resins. Examples of 'tlieseresins' are asioh lows:

Example 7 Four parts of the reaction product 0113.6 mols ethylene glycol, 3 mols diethylene glycol, l ,.rnols fumaric acid, and 2 mols phthalic anhydride, were copolymerized with 1 part of diallyl phthalate.

Example 2 Four parts of the reaction product of 3.6 mols of ethyleneglycol, 3 mols diethylene glycol, 4 mols fumaric acid, and 2 mols phthalic anhydride were copolymerize'd with 2 parts of styrene.

Resins of this type are preferably catalyzed with a peroxide, 1% benzoyl peroxide being very satisfactory for this purpose.

The paper used in practicing this invention is selected to "give optimum transparency when combined with the resin in the surface film. It should be absorbent and should be made from fibers having a refractive index approaching that of the resin, have good uniformity of fiber distribution, and be free from foreign particles. In no case should the optical path difierence between adjacent paths through the fiber-resin complex be more than half the wavelength "of visible light. (The optical path difference is 'de- 5 fined as height of the heterogeneity multiplied heterogeneity and its matrix.)

fibers, Hurlbut 723, a mil sheet of chemical coniferous wood fibers; and, a paper made similar to Aldex B but with acetate rayon fibers and fine grass fibers has been found suitable. It should be noted, however, that the papers made from synthetic fibers are preferable, since they result in greater clarity of the surface film for many reasons such as optical homogeneity and absence of irregularities and capillaries inherent in natural fibers.

It is believed that the invention will be more 'fully understood from the following more specific and detailed description of the invention.

Example 3 The plastic resin composition of'E-xample 1 was applied to a polished steel press plate by knifecoating with a spread of -50 grams per square foot, the resin being catalyzed with 1% benzcyl peroxide. A specially selected paper in the form of a 4 mil sheet composed of approximately 90% viscose rayon fibers and 10% fine grass fibers, uniformly distributed, and free from foreign particles, was smoothed onto the resin coated press plate and heated in an oven until the resin was partially polymerized, 18 minutes at 75 C. being sufiici'ent for plates 8 x 8" x .030, whereas to minutes at C. was requiredfor plates 30" x 30 x 0.100. [k /23' veneer of walnut was coated with the composition of Example 1 to the extent of approximately 20 grams per square foot, the resin being catalyzed with 1% benzoyl peroxide, and permitted to gel as above described; the time required for suitable .gelation being 15-45 minutes at 75-85" (7., depending upon the size of J the veneer panel. The press plate was then superimposed upon the coated wood veneer, and assembly pressed at P. S. I. on the small panel and 175 P. S. I. on the large panel for 15-30 minutes. at, a temperature of C. The assembly was removed from the press and the plate stripped from the panel, it being unnecessary to first cool the press. Similar surfaces were obtained by repeating the above experiment with the resin of Example 2, and with other Wood veneers, such as mahogany- I l-Iigher or lower pressures may be used in pressing the assembly, depending upon the type of wood, size of the panel, accuracy of alignment of the platens, and the like. Likewise, higher temperature may be employed, since the resin is not sensitive, to overcure, and when so done, shorter periods of pressing are used.- It is recommended, however, that temperatures under C. be used.

The addition of approximately 0.4% of a 30% solution of para tolueno sulfonic acid in ethylene glycol per 100 grams of resin as'an accelerator is recommended since it is a definite aid in obtaining a uniform gel of the resin over the entire area of the coated material, and it effects a reduction ingel time of approximately 50%, i. e., from 45 to 50 minutes, as indicated in Example 3, to 25 to 30 minutes. 1

It should also be pointed out that the time required to obtain the correct degree of gelation will necessarily vary with conditions such as the type and efllciency of the oven used and if the wood is stained and filled, any accelerating or inhibiting effect these materials may i have on theresin. I

' veneer.

Example 4 The procedure of the above Example 3 was repeated by assembling resinous adhesive coated wood veneers to provide a core, upon which was placed the veneer of walnut having the pregell peroxide catalyzed resin coat, and the pregelled resin and paper covered press plate. In this Way,

the transparent finish was applied to plywood, with the gluing of the plywood veneers, that is, when the plywood was made.

Example 5 Example 4 was repeated by employing a 0.001

K sheet of sodium hydroxide etched aluminum foil placed between sheets of kraft paper impregnated with low pressure phenolic resin. This assembly was positioned beneath the walnut A complete cigarette-proof panel was prepared in this manner, even though the veneer was /2 of an inch thick.

The invention is not intended to be limited to the process wherein the resin is pregelled on the press. plate, but it is also intended to include the process wherein the paper is impregnated with the resin and pregelled by heating, such as pass-v ing. it through an oven or a battery of infrared lamps after Which it is placed directly on the wood or other hardboard surface. It should be further pointed out, however, that dyes, pigments, and the like, may be incorporated in the resin to obtainclear colored or opaque colored surfaces when they are desired rather than clear transparent surfaces. In the case of opaque surfaces, the refractive index of the fiber becomes of little importance as likewise do the inhomogeneities and capillaries of natural fibers. As has previously been pointed out, pleasing modifications of the surfaces can be obtained by using embossed press plates in the pressing procedure. Due to the fibrous substrata used in the protective overlay,

have capillaries and irregularities of surface due to their living functions, and are therefore not as easily adaptable to utility in this invention as are the synthetic fibers which are more optically homogeneous. However, the synthetic fibers do not lend themselves to easy felting, and usually a paper of mixed natural and synthetic fibers will be employed. In further discussion of the paper it is advisable to employ a specially prepared paper wherein the fibers are uniformly distributed, and preferably horizontally orientated.

Other clear thermosetting polyester resins of light color having refractive indices in the cured state approximating that of the fibers in 'the substrata may be suitably employed in this invention. They may be roll or knife-coated on the press plate, wood veneer, and paper. The diallyl phthalate resins may also be employed with a suitable solvent to reduce the viscosity suificiently to permit spray or brush coating;

Resins of the type illustrated in Examples 1 and 2 may be modified with flexible resins to enhance flexibility of the surface finish.

This invention is particularly useful in the production of superior quality finishes for table tops, desk tops, panelling, doors, cabinets, and other like applications where durable finishes which retain the natural beauty of the Wood, or opaque durable finishes, are desired. Likewise, boat hulls and other boat parts may be finished according to this invention using suitable modifications of the process described herein. A Wood veneer surfaced according to the teaching of this invention and bonded to a core of a plurality of phenolic impregnated kraft paper has many commercial uses. Also, aluminum foil may be bonded in this assembly between the veneer and core if desired. In general, the invention can be used to obtain superior products in many applications where conventional surface coatings are now used.

We claim:

1. A process for preparing a surface finish comprising coating a clear transparent press plate and a Wood veneer with a clear thermosetting polyester resin, smoothing a substrata of uniformly distributed optically homogeneous synthetic resin fibers over said resin coated press plate, said resin and fibers having approximately the same refractive indices, superimposing said press plate on said veneer, and bonding the veneer and substrata under heat and pressure.

2. A process for preparing a surface finish comprising coating a clear transparent polished steel press plate with a peroxide catalyzed clear thermosetting unsaturated polyester resin, smoothing thereon a paper in the form of a 4 mil sheet composed of approximately 90% viscose rayon fibers and fine grass fibers uniformly distributed and free from foreign particles, heating said paper covered resin coated press plate until the resin is partially polymerized, coating the surface to be finished with the peroxide catalyzed clear thermosetting unsaturated polyester resin and heating to partially polymerize said resin, and pressing said press plate on said surface to be finished accompanied by heat and pressure, said resin comprising the copolymer of diallyl phthalate and the reaction product of a polyhydroxy alcohol and dicarboxylic acid.

3. A process for preparing a surface finish comprising coating a clear transparent press plate and a wood to be surfaced with a clear thermosetting polyester resin, smoothing a substrata of uniformly distributed optically homogeneous synthetic resin fibers over said resin coated press plate, said resin and fibers having approximately the same refractive indices, superimposing said press plate on said wood, and bonding the wood and substrata under heat and pressure, said resin comprising the copolymer of diallyl phthalate and the reaction product of ethylene glycol, diethylene glycol, fumaric acid and phthalic anhydride.

4. A process for preparing a surface finish comprising coating a clear transparent press plate and a wood veneer with a clear thermosetting polyester resin, smoothing a substrata of uniformly distributed optically homogeneous synthetic resin fibers over said resin coated press plate, said resin and fibers having approximately the same refractive indices, superimposing said press plate on said veneer, and bonding the veneer and substrata at the temperature of approximately 105 C. and at pressure of from about 100 to about 200 P. S. I.

5. A process for preparing a surface finish comprising coating a clear transparent polished steel press plate with a peroxide catalyzed clear thermosetting unsaturated polyester resin with a spread of about 45 to about 50 grams per square foot, smoothing thereon a paper in the form of a 4 mil sheet composed of approxmately acetate rayon fibers and 10% fine grass fibers uniformly distributed and free from foreign particles, heating said paper covered resin coated press plate until the resin is partially polymerized, coating the surface to be finished with a peroxide catalyzed clear thermosetting unsaturated polyester resin with a spread of about 20 grams per square foot, and heating to partially polymerize said resin, and pressing said press plate on said surface to be finished for sufficient time to cure the resin at the pressing temperature and pressure, said resin comprising the copolymer of diallyl phthalate and the reaction product of polyhydroxy alcohols and dicarboxylic acids.

6. A process for preparing a clear, transparent surface finish comprising gelling the thermosetting polyester resin on a paper, comprised essentially of optically homogeneous synthetic resin fibers of approximately the same refractive index as the resin, coating the surface to be finished with said resin and gelling the same, and bonding the paper to the surface by the application of heat and pressure, said paper having a thickness of at least 4 mils.

7. A process for preparing a surface finish comprising pre-gelling a thermosetting polyester resin impregnated paper, comprised essentially of optically homogeneous synthetic resin fibers of approximately the same refractive index as the resin, coating the surface to be finished with said resin and pre-gelling the same, and bonding the paper to the surface by the application of heat and pressure, said resin comprising the copolymer of styrene and the reaction product of ethylene glycol, diethylene glycol, fumaric acid and phthalic acid anhydride, said paper having a thickness of at least 4 mils.

8. A process for preparing a clear, transparent surface finish comprising gelling a thermosetting polyester resin on a paper, comprised essentially of optically homogeneous synthetic resin fibers of approximately the same refractive index as the resin, coating the surface to be finished with said resin and gelling the same and bonding the paper to the surface by the application of pressure and heat at a temperature between 75 C. and 0., said paper having a thickness of at least 4 mils.

DONALD G. PATTERSON. WILLIAM F. TURNER.

REFERENCES CITED The following references are of record in the file of this patent:

Green Feb. 7, 1950 

1. A PROCESS FOR PREPARING A SURFACE FINISH COMPRISING COATING A CLEAR TRANSPARENT PRESS PLATE AND A WOOD VENEER WITH A CLEAR THERMOSETTING POLYESTER RESIN, SMOOTHING A SUBSTRATA OF UNIFORMLY DISTRIBUTED OPTICALLY HOMOGENEOUS SYNTHETIC RESIN FIBERS OVER SAID RESIN COATED PRESS PLATE, SAID RESIN AND FIBERS HAVING APPROXIMATEDLY THE SAME REFRACTIVE INDICES, SUPERIMPOSING SAID PRESS PLATE ON SAID VENEER, AND BONDING THE VENEER AND SUBSTRATA UNDER HEAT AND PRESSURE. 